{"id":6292,"date":"2024-08-06T11:27:17","date_gmt":"2024-08-06T09:27:17","guid":{"rendered":"https:\/\/www.pschatzmann.ch\/home\/?p=6292"},"modified":"2024-07-30T21:57:50","modified_gmt":"2024-07-30T19:57:50","slug":"testing-the-audio-pwm-output-on-a-stm32h7","status":"publish","type":"post","link":"https:\/\/www.pschatzmann.ch\/home\/2024\/08\/06\/testing-the-audio-pwm-output-on-a-stm32h7\/","title":{"rendered":"Testing the Audio PWM output on a STM32H7"},"content":{"rendered":"

In my last blog<\/a>, I described the analog audio output<\/strong> using the Arduino Audio Tools library<\/a>: The STM32H743VIT6<\/strong> microcontroller is quite powerful but we only have max 2 DAC pins<\/strong> available!<\/p>\n

This restriction falls when we use PWM<\/strong>: We use a PWM frequency above the hearing range (30khz) and modulate the PWM Duty Cycle with the audio signal.<\/p>\n

Compared to the demo pwm sine example<\/a>, I increased the sample rate<\/strong> to 44100 and the channels<\/strong> to 2 and I defined the two output pins<\/strong>.<\/p>\n

#include \"AudioTools.h\"\n\nAudioInfo info(44100, 2, 16);\nSineWaveGenerator<int16_t> sineWave(32000); \nGeneratedSoundStream<int16_t> sound(sineWave);  \nPWMAudioOutput pwm;                  \nStreamCopy copier(pwm, sound);    \nint pins[] = {PA1, PA5};\n\n\nvoid setup() {\n  Serial.begin(115200);\n  AudioLogger::instance().begin(Serial, AudioLogger::Warning);  \n\n  \/\/ setup sine wave\n  sineWave.begin(info, N_B4);\n\n  \/\/ setup PWM output\n  auto config = pwm.defaultConfig();\n  config.copyFrom(info);\n  config.setPins(pins);\n  pwm.begin(config);\n}\n\nvoid loop(){\n  copier.copy();\n}\n<\/code><\/pre>\n
Here is result from an oszilloscope:<\/p>\n
\"\"<\/p>\n
It seems that the output signal between the different channels are not quite in synch<\/strong> but apart from this, it seems to work perfectly.<\/p>\n
To turn this into a proper sine wave on the oscilloscope, we would need to add a low pass filter<\/a>. But you can connect some earphones directly, because your ears will act as low pass filter since humans can only hear up to 17’000hz and this decreases when we get older.<\/p>\n","protected":false},"excerpt":{"rendered":"
In my last blog, I described the analog audio output using the Arduino Audio Tools library: The STM32H743VIT6 microcontroller is quite powerful but we only have max 2 DAC pins available! This restriction falls when we use PWM: We use a PWM frequency above the hearing range (30khz) and modulate […]<\/p>\n","protected":false},"author":1,"featured_media":6293,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_crdt_document":"","_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"footnotes":""},"categories":[20,22],"tags":[47],"class_list":["post-6292","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-arduino","category-machine-sound","tag-stm32h7"],"yoast_head":"\nTesting the Audio PWM output on a STM32H7 - Phil Schatzmann<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.pschatzmann.ch\/home\/2024\/08\/06\/testing-the-audio-pwm-output-on-a-stm32h7\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Testing the Audio PWM output on a STM32H7 - Phil Schatzmann\" \/>\n<meta property=\"og:description\" content=\"In my last blog, I described the analog audio output using the Arduino Audio Tools library: The STM32H743VIT6 microcontroller is quite powerful but we only have max 2 DAC pins available! This restriction falls when we use PWM: We use a PWM frequency above the hearing range (30khz) and modulate […]\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.pschatzmann.ch\/home\/2024\/08\/06\/testing-the-audio-pwm-output-on-a-stm32h7\/\" \/>\n<meta property=\"og:site_name\" content=\"Phil Schatzmann\" \/>\n<meta property=\"article:published_time\" content=\"2024-08-06T09:27:17+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/www.pschatzmann.ch\/wp-content\/uploads\/2024\/07\/pwm.png\" \/>\n\t<meta property=\"og:image:width\" content=\"1020\" \/>\n\t<meta property=\"og:image:height\" content=\"524\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/png\" \/>\n<meta name=\"author\" content=\"pschatzmann\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"pschatzmann\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"2 minutes\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2024\\\/08\\\/06\\\/testing-the-audio-pwm-output-on-a-stm32h7\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2024\\\/08\\\/06\\\/testing-the-audio-pwm-output-on-a-stm32h7\\\/\"},\"author\":{\"name\":\"pschatzmann\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/#\\\/schema\\\/person\\\/73a53638a4e34e8373405fd737dac9b1\"},\"headline\":\"Testing the Audio PWM output on a STM32H7\",\"datePublished\":\"2024-08-06T09:27:17+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2024\\\/08\\\/06\\\/testing-the-audio-pwm-output-on-a-stm32h7\\\/\"},\"wordCount\":173,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/#\\\/schema\\\/person\\\/73a53638a4e34e8373405fd737dac9b1\"},\"image\":{\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2024\\\/08\\\/06\\\/testing-the-audio-pwm-output-on-a-stm32h7\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/www.pschatzmann.ch\\\/wp-content\\\/uploads\\\/2024\\\/07\\\/pwm.png\",\"keywords\":[\"STM32H7\"],\"articleSection\":[\"Arduino\",\"Machine Sound\"],\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2024\\\/08\\\/06\\\/testing-the-audio-pwm-output-on-a-stm32h7\\\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2024\\\/08\\\/06\\\/testing-the-audio-pwm-output-on-a-stm32h7\\\/\",\"url\":\"https:\\\/\\\/www.pschatzmann.ch\\\/home\\\/2024\\\/08\\\/06\\\/testing-the-audio-pwm-output-on-a-stm32h7\\\/\",\"name\":\"Testing the Audio PWM output on a STM32H7 - 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